Method of making reinforced composite structures

ABSTRACT

PROCESS FOR MAKING COMPOSITE STRUCTURES FORMED OF REINFORCEMENT STRANDS EMBEDDED IN A METAL MATRIX IN WHICH ESSENTIALLY CYLINDRICAL CONTINUOUS FILAMENTS HAVING A DIAMETER WITHIN THE RANGE OF 5-200 MICRONS ARE WOUND IN LAYERS AROUND A FORM WHILE THE MATRIX METAL IS SUBSTANTIALLY SIMULTANEOUSLY DEPOSITED BETWEEN SUCCESSIVE LAYERS AND BETWEEN ADJACENT STRANDS IN A GIVEN LAYER, THE FILAMENTS BEING GUIDED TO THE FORM AT A RATE SUFFICIENT TO GIVE A CLEARANCE BETWEEN ADJACENT FILAMENTS EQUAL TO AT LEAST ONE-HALF THE FILAMENT DIAMETER AND THE AMOUNT OF MATRIX METAL BETWEEN LAYERS BEING SUFFICIENT TO GIVE A SIMILAR CLEARANCE BETWEEN SUCCESSIVE LAYERS EQUAL TO AT LEAST ONE-HALF THE FILAMENT DIAMETER, THE AGGREGATE OF THE VOLUME OF THE FILAMENTS IN THE COMPOSITE STRUCTURE NOT EXCEEDING ABOUT 60% OF THE TOTAL VOLUME THEREOF. THE MATRIX METAL CAN BE DEPOSITED IN VARIOUS WAYS, INCLUDING ELECTROPLATING AND VAPOR DEPOSITION.

United States Patent 1 Withers 14 Oct. 2, 1973 METHOD orMAKINGREINFORCED COMPOSITE STRUCTURES [76] Inventor: James C. Withers,1612 Greenbriar 7 Court, Reston, Va. 221 Filed: May 29, 1969 [211 App].No.: 828,856

Related US. Application Data [63] Continuation-impart of Ser. No.486,078, Sept. 9,

1965, abandoned.

[52] US. Cl 204/16, 117/130 R, 156/169,

I 156/173, 204/9 [51] Int. Cl. C23b 7/02, C23b 7/00 [58] Field of Search204/3-9,

[56] References Cited UNITED STATES PATENTS 2,699,415 1/1955 Nachtrnan117/130 2,718,583 9/1955 Noland et 156/173 2,744,043 5/1956 Ramberg156/172 2,783,174 2/1957 Stephens 156/172 3,313,664 4/1967 Reinhart, Jr.156/155 FOREIGN PATENTS OR APPLICATIONS Germany 204/3 PrimaryExaminer-John H. Mack Assistant Examiner-T. Tufariello AttorneyWilliamJ. Daniel 5 7 ABSTRACT ing a diameter within the range of 5-200 micronsare wound in layers around a form while the matrix metal issubstantially simultaneously deposited between successive layers andbetween adjacent strands in a given layer, the filaments being guided tothe form at a rate sufficient to give a clearance between adjacentfilaments equal to at least one-half the filament diameter and theamount of matrix metal between layers being sufficient to give a similarclearance between successive layers equal to at least one-half thefilament diameter, the aggregate of the volume of the filaments in thecomposite structure not exceeding about 60% of the total volume thereof.The matrix metal can be deposited in various ways, includingelectroplating and vapor deposition.

4 Claims, 8 Drawing Figures PATENTH] DDT 21975 SHEET 2 BF 3 INVENTORJAMES 0. WITH ERS ATTORNEYS PATENTEUUET 21915 3.763.001 w SHEU 30F 3Fig.8

JAMES C. WIT'HERS ATTORNEYS INVENTOR METHOD OF MAKING REINFORCEDCOMPOSITE STRUCTURES This application is a continuation-in-part of myapplication Ser. No. 486,078 filed Sept. 9, 1965, and now abandoned.

This invention relates to novel processes for making reinforced-matrixcomposite structures, and also to novel filament-reinforced structuresmade according to these processes, which structures have particularutility in applications where high-strength and low weight is required,for instance, in outer-space hardware.

The present state of the art teaches processes for making reinforcedstructures wherein both the processes and the resulting structuressuffer from serious defects and/or limitations. Several of these priorart techniques are as follows:

The prior art liquid-infiltration technique involves forming of a metalmatrix by raising the temperature of the matrix metal above its meltingpoint to put it into a liquid state. The reinforcement filaments orelements are preformed into an array within a mold into which the liquidmatrix metal can be poured to surround and infiltrate this array of,elements. One apparent disadvantage of this particular process residesin the difficulty involved in orienting the reinforcements in the arrayand holding the desired orientation while the molten matrix material ispoured thereinto. Even relatively simple forms such as cylindrical,conical, spherical, or rectangular forms are very difficult topre-shape, and it is also difficult, after they are shaped, to make themolten metal completely infiltrate the reinforcements. Another veryserious limitation of this type of process is that, because of thesustained high temperature required to melt most useful matrix metals,there are relatively few filamentary reinforcements which are notdamaged either by melting, by thermalshock, or by chemical interactionwhen the metal is poured thereonto at an elevated temperature. Forinstance, it would be impossible to place fiber glass reinforcementswithin most matrix metals by this process. Another serious limitationresides in the fact that many of the matrix metals which would be usefulunder severe operating conditions, for instance in motor parts, cannotbe melted at convenient temperatures to permit their infiltration intomatrix reinforcements.

Another class of prior art technique involves powdered-metallurgymethods which are most frequently used at present to produce metalmatrix composites. According to this prior art teaching the matrix metalis mixed in powdered form and consolidated at an elevated temperatureand/or pressure, or by sintering. Obviously, the reinforcement filamentsor elements must be arranged within the powdered metal matrix before itis consolidated, and this leads to serious difficulties caused byphysical damage to the reinforcements as a result of pressing the matrixduring consolidation. Accordingly, relatively hard or brittlereinforcing elements cannot be used with this technique. Moreover, it isvery difficult to orient the reinforcing agents, or to place them undereven slight tension for the purpose of making sure that they extend indesired directions so that they can properly reinforce the compositestructure in predetermined stress directions. Another seriousdisadvantage resides in the high temperatures necessary forconsolidation, which temperatures can cause undesirable chemicalinteractions between matrix and reinforcing materials, thereby resultingin inferior composite structures. Moreover, it is very difficult to formcomponents having curved or complex contours of types which are bestreinforced by continuous filaments.

The novel processes according to the present invention involve themaking of reinforced matrix composites by depositing the matrix materialupon a moving form or mandrel to which filamentary reinforcements areapplied, for instance by rotating the mandrel and winding thereinforcements thereon while the matrix material is being deposited. Thedeposition of the matrix material is accomplished at low temperaturesfor instance by electroplating, vaporplating (sometimes called gasplating), vacuum evaporation, or even plasma or flame sprayingtechniques which can be used even with reinforcing materials havingrelatively low melting points. Although the present novel process doesnot lend itself to the application of reinforcing members in just anydirection whatever, the winding of reinforcements onto rotating forms isextremely advantageous, where conveniently done, because it applies thereinforcements as continuous filaments; because it permits theapplication of reinforcements which are oriented in circumferentialdirections; and because it provides reinforcements whose density can beprogrammed to place the filaments closer together in zones of highstress and further apart in zones of low anticipated stress. Moreover,the spacings of the filaments can be controlled very accurately, whichis an important aspect of the invention, and the filaments can betensioned to provide a structure which is prestressed.

It is not necessary that the reinforcements be wound exactlysimultaneously with the deposition steps. The same result can beachieved by alternating winding and deposition so as to wind a layer ofreinforcement filaments around a suitable form, then deposit matrixmaterial on the surface and between and upon the filament layer and soon.

Another important advantage of the present process is that the filamentscan be spaced in a precision manner so as to introduce the clearancewith such accuracy therebetween essential to the achievement of a highquality composite structure.

Another important advantage of the present invention is that the windingrate and the winding tension can be separately and independentlyadjusted in relationship to the rate at which matrix material depositionoccurs, thereby providing means by which the ratio of reinforcingmaterial to the matrix material can be conveniently controlled so as tonot exceed the maximum relationship capable of giving satisfactoryproducts.

Another advantage of the present process is that unusual combinations ofreinforcing elements with matrix metals can be accomplished because ofthe low temperatures at which the process is carried out. In otherwords, the reinforcing materials are not required to enter into anyphysical or chemical interaction with the matrix material where thetemperature is not elevated. Even where the deposition is accomplishedby plasma or flame spraying, low-melting point reinforcement materialcan be successfully used by confining the spray to a sector of themandrel or form which is small as compared with its circumference, sothat the heating is brief, as distinguished from sustained heating.Typical reinforcement materials include tungsten wire, steel wire,beryllium wire, glass filament, quartz filament,

boron filament, silicon carbide filament, titanium boride filament,boron carbide filament, boron nitride filament, etc. Some examples ofmatrix materials include aluminum, magnesium, titanium, nickel, andother materials, including alloys thereof. Specific examples ofcomposites made according to the present invention are given below.

The present process has produced unexpectedly superior results which insome cases have actually exceeded the theoretical values which werepredicted Y on the basis of prior experience and theory. Ordinarily,

the properties of a composite cannot be expected to exceed the sum ofthe properties of each component when weighted according to thepercentage of the component which is present. As an example, a compositecontaining 25 percent of 500,000 psi boron filament and 75 percent ofl25,000 psi nickel matrix would not be expected to have a tensilestrength higher than 25 percent X 500,000 plus 75 percent X 125,000218,000 psi. Composites made by powdered metallurgy or liquidinfiltration prior art techniques exhibit strength values far less thanthe values theoretically,

predicted. However, the composites produced by the present depositionprocesses exhibit strength values at least as good as theoreticallypredicted, and in many cases exhibit unexpectedly superior properties.As an example, the boron nickel composite referred to above had atensile strength of 300,000 psi, rather than 218,000 psi as predicted.

Consequently, the present novel process produces composite structuresincorporating continuous filaments which can be oriented and accuratelyspaced and tensioned during formation of a wide variety of contours; andin which the reinforcements can be con veniently and smoothly variedaccording to their density; and in which the reinforcements suffer nodamage or undesired interaction during fabrication; and in which thecomposites exhibit theoretically expected, or even higher strengthvalues.

It has been discovered that in the formation of composites structures ofthe type in question, one of the most serious problems is the'existenceof voids within the body of the structure due to the failure of thematrix metal to be deposited completely around the reinforcementfilaments. This problem is especially troublesome where the filamentsare essentially circular in cross-section, as contemplated by thisinvention, as the crevices underlying the circular sides of thefilaments, i.e. the angle included between the circular sides and ahorizontal plane extending tangentially at the lower side of thestrands, are difficult to fill with the metal. Moreover, if the metal isdeposited in these areas, it can grow in a different manner than thatdeposited above and between the filaments with the result that voids canoccur at the junction where the depositions meet. By careful selectionof the size of the filaments, regulation of the delivery of thefilaments to the form to maintain minimum clearances between adjacentfilaments in a layer and between successive layers, and imposition of amaximum on the proportion by volume of filaments in the total compositestructure, solid void-free structures uniformly and reproduciblyexhibiting the superior properties heretofore noted can be produced.

The nature of the present invention will be more fully revealed by thefollowing detailed description and the accompanying drawings wherein:

FIG. 1 is a perspective view of apparatus for winding reinforcementfilaments on a mandrel form and electroplating the matrix metal thereon,the plating tank being partly broken away to show its interior;

FIG. 2 is a perspective view of apparatus for either vapor plating orvacuum deposition of a matrix material on a mandrel form and for windingfilamentary reinforcements thereon;

FIG. 3 is a partial perspective view of apparatus for producing on amandrel form a wound-reinforcement composite including means forspraying the matrix material on the mandrel in the vicinity of thewinding;

FIG. 4 is a partial perspective view of apparatus for applyingfilamentary reinforcements to a dome-end vessel within a matrixdeposition zone;

FIG. 5 is a partial perspective view of apparatus for cross-windingreinforcements upon a polygonal mandrel form in a deposition zone;

FIG. 6 is a partial cross-sectional view through a composite made by theapparatus shown in FIG. 5;

FIG. 7 is a partial perspective view showing apparatus for windingreinforcements upon a nozzle-shaped mandrel; and I FIG. 8 is across-sectional view taken through a nozzle made by theapparatus shownin FIG. 7, and wherein the reinforcements are non-uniformly distributedso as to have maximum concentration near the throat constriction of thenozzle.

Referring now to the drawings, FIG. 1 shows apparatus for making acylindrical reinforced composite, the machine including a supportingframe 1 having a deposition tank 2 mounted thereon opposite a mandreldrive head 3 including an appropriate motor M with a speed control N,and having a gear reducer (not shown). The deposition tank 2 has a sealbushing 4 through which a shaft 5 coupled to the gear reducer extendsinto the tank 2. This shaft supports a mandrel form 6 whose externalshape conforms with the desired shape of the finished product. Thedeposition tank 2 includes windows 2a and a packing gland 7 whichsupports and guides a reciprocatory tube 8. Another gland similar to thegland 7 is located at the left side of the deposition tank 2 and passesthe other end of the tube 8 to a supporting yoke 9 which is slidableback and forth upon the frame 1. The yoke supports a filament-feed spool10 which stores the filament wire 11 in supply adequate to complete thejob, and this filament wire passes from the spool into the tube 8through a seal 12 within the tube and to a small guide roller 13 whichis joumalled in the wall of the tube 8. The roller 13 can be movedlongitudinally back and forth parallel to the axis of the shaft 5 byreciprocating the tube 8 in the glands 7.

Such reciprocation is accomplished by moving the yoke 9 back and forthalong the frame 1 either manually by turning the hand-wheel 13 orautomatically by depressing the lever 15 so as to clamp a split nut (notshown) on the lead screw 14 in a manner well-known in the lathe art. Thelead screw 14 is rotated by an appropriate gear (not shown) locatedwithin the drive housing 3, and means D is provided for adjusting therate of rotation, and/or the direction of rotation, of the lead screw 14relative to the shaft 5.

Within the deposition tank 2 there is located an anode l6, and directcurrent is applied between the cathode-mandrel 6 and the anode 16through appropriate wiring from a battery 17, the current beingcontrollable in any suitable manner via the variable resistor 18.

The tank 2 is at least partially filled with a suitable electrolyte l9,specific examples thereof being given below. The mandrel 6 has aconductive surface 611 which may be obtained in one of a number ofsuitable ways, for instance by spraying, or alternatively the mandrelmay be precoated or metallized before insertion into the deposition tank2.

If the mandrel is not to be removed from the finished composite product,then it is only necessary that the mandrel have the desired shape and asuitable surface on which deposition can be accomplished. However, if itis desirable to make a hollow composite structure on the presentapparatus, then the mandrel must be re movable from within the finishedproduct. For example, the mandrel can be made of wax and can have apowdered graphite surface applied thereto in order to render itconductive. With this type of structure, when the composite matrixproduct has been completed by plating, the mandrel can easily be removedfrom the interior thereof by melting the wax. There are also a number ofother plastics whose surfaces can be made conductive by thepro-application of metal. Metal mandrels have also been used toadvantage, and have been made of aluminum or steel, or of low-meltinglead, tin, or other eutectic alloy. These mandrels are preshaped to thedesired configuration, and after the composite product has-been formedthereon, in some cases the mandrels are removed by mechanicalseparation, by chemical dissolution, or by melting. Sometimes the outersurface of a component itself forms the mandrel onto which a reinforcedmatrix is further applied which is not to be removed therefromsubsequently. See, for example, the disclosure of the reinforced vesselas deposited in FIG. 4.

FIG. 2 shows a deposition chamber having several access openings, whichare sealed by appropriate covers 20a, 20b, 20c, etc. A vacuum pumplocated within the housing labeled P is attached to the lower opening ofthe housing 20 in order to maintain the latter substantially evacuated.Within the deposition chamber 20 is located a mandrel 21 supported on adrive arm 22 containing suitable mechanism for rotating the mandrel, themechanism not being illustrated in the present drawing. The filamentaryreinforcements 23 are taken from a storage spool 24 located within thechamber, and these reinforcements are guided onto the mandrel 21 by aguide roller 25 moved axially of the mandrel 21 by mechanism (notshown). If the vacuum evaporation process is to supply the matrix metalto the mandrel 21, a metal vapor source 26 is placed within the chamber20 and heated by suitable heater means 260. On the other hand, theillustrated apparatus can supply the matrix metal by a vapor platingprocess, then the gas including the appropriate vapor can be suppliedfrom a source S through the cover 200 via a pipe 27 having an internalextension and nozzle 27a for directing the gas toward the winding areaon the surface of the mandrel. Various mechanical mechanisms can be usedto supply proper translation to the guide 25, and/or to the nozzle 27during the deposition process, the specific mechanical shaft meanshaving no patentable significance in the present invention.

FIG. 3 shows metal spray apparatus for building up matrix metal upon amandrel 30 which can be located within a suitable deposition zone. Means(not shown) are provided to rotate the shaft 31 which supportsthemandrel opposite a spray nozzle 32 and opposite a translating block 33including guide roller means 34 over which one or more filaments 35 canpass. The nozzle can be supported on an arm 36 which is fixed to theblock 33 so that the spray nozzle 32 applies the spray to the generalarea where winding of the reinforcements is being accomplished on themandrel 30. The traverse block 33 can be supported on a rod 37 and upona lead screw 38 which is also rotated by suitable drive means (notshown). The spraying of the matrix material against the wound filamentsof course heats them, but only briefly in a localized zone which quicklypasses away from the spray nozzle 32 and therefore can cool rapidly, andbefore the filaments 35 are damaged by the heat from the spray nozzle.

FIG. 4 shows a more complex filament winding mechanism intended to belocated within a deposition zone. This mechanism includes a motor Msupport on a stationary frame 40 and driving a shaft 41 to which a largecam 42 is attached. Means (not shown) transmits drive from the motor Mthrough an arm 41a below the cam 42 to rotate a shaft 43 which supportsa mandrel 44, the mandrel in this example comprising a substantiallyclosed vessel which rotates opposite the guide roller 45 which serves toguide reinforcement filaments 46 onto the mandrel surface. The mandrel44 is rotated about the vertical shaft 41, and also about the inclinedshaft 43 so that the filamentary reinforcements are evenly spaced asthey are wound on the outer surface of the vessel 44. The guide roller45 is supported upon a frame 47 which can reciprocate on a rod 48, suchreciprocation being accomplished by contact of the cam follower 47a withthe periphery of the cam 42. If desired, an additional freedom of motionof the support 47 can be provided by movement of the frame 47 along therod 49 in response to the other drive means (not shown).

FIG. 5 shows still another winding mechanism for use in a vapordeposition zone, illustrating a polygonal mandrel 50 supported upon ashaft 51 which is rotated by a suitable drive mechanism (not shown). Aguide block 52 is supported upon a rod 53 and a lead screw 54 which isalso rotated by suitable drive mechanism (not shown). Filamentaryreinforcement 55 is delivered from a supply spool over a guide roller56, and in this case the translating guide block 52 is caused totraverse alternately in opposite directions parallel to the axis of thedrive shaft 51 so as to wind successive layers of cross reinforcements55 upon the mandrel 50 while the deposition of the matrix material (notshown) is being accomplished.

FIG. 5 shows a cross-sectional view taken through a resulting compositestructure, and showing the matrix material with crossed reinforcementsembedded therein, the reinforcements in one direction being labeled 61,and the reinforcements running in the normal direction being labeled 62.This apparatus forms a particularly well reinforced composite in whichthe reinforcements are crossed either at right angles or at acute anglesif desired, and depending upon the directions and rates of rotation ofthe shafts S1 and 54 with respect to each other, the spacings betweenlayers of reinforcements being determined by the rate of deposition ofthe matrix material 60 as compared with the rates of rotation of theshafts 51 and 54.

FIG. 7 shows still another winding means including a shaft driven bysuitable driving means (not shown) and supporting a nozzle-shapedmandrel 71 having a necked-down central portion. The matrix material isdeposited on the surface of the mandrel 71, by deposition means (notshown) and filamentary reinforcements 72 are wound thereon from a supplyreel 74, the distribution of the reinforcements 72 being controlled by aguide roller 73 which may be either manually or automatically translatedin a direction parallel with the shaft 70, but at a non-uniform rate toprovide unequal distribution of the reinforcements within the depositionzone of the machine.

FIG. 8 shows a resulting structure including matrix material 80 andreinforcements 81 distributed therewithin, and having the greatestconcentration of reinforcement in the vicinity of the restricted neck ofthe nozzle-shaped composite. This drawing is intended to illustrate themanner in which distribution of the reinforcements can 'be selectivelyaccomplished during manufacture of composite structures.

As mentioned briefly earlier, the reinforcement filaments contemplatedby this invention are generally circular in cross-section. Filaments ofthis configuration are readily available in a variety of materials and awide range of sizes and can be obtained at minimum cost. Moreover, theirsymmetry and uniformity confer particularly desirable load-bearingproperties in the present composite structures since stress imposed uponthem is uniformly distributed, avoiding points of uneven stress whichcan lead to failure in use. In any event, the operating conditionsenvisioned herein have been established in conjunction with filaments ofthis configuration in order to overcome difficulties peculiarlypresented by the use of such filaments for composite formation.

Although large filaments might normally be expected to give the bestresults here due to their greater strength and reinforcement value, suchhas not been found to be the case. Rather the size of the filaments havebeen found to be an important factor in the achievement of solid, highquality composites with very small filaments being a virtual requirementfor such products. If the filament diameter very much exceeds about 200microns, the depth of the included spaces lying under the maximumprojections of each filament exceeds the lateral penetrating capacity ofpractical deposition techniques. Below this limit, as a general rule thesmaller the filament the better the results that are obtained subject tothe practical qualification that the filament size be consistent withacceptable feeding requirements. At diameters of less than aboutmicrons, filaments of the type in question are extremely difficult tohandle for purposes of feeding, guiding and other manipulativeoperations and any further improvement in deposition quality is morethan offset by such ditficulties. Preferably, the lower limit ofdiameter is 0.5 mil or about 12 microns.

If very small filaments are to be employed, they are better used inloose bundles or tows which must be essentially twist-free in order tospread out in a substantially single thickness layer which applied undertension to the mandrel form. In this condition, such bundles function asaggregates of single strands as far as this process is concerned exceptthat they are much more readily handled.

It is crucial to the present invention that the helical windingsconstituting the layers of reinforcement not be laid down in extremelyclose, tight or contacting relation as penetration of the matrix metalbetween adjacent windings to form the desired solid embedments isimpossible under such circumstances. The superior results characteristicof this invention are dependent upon' the maintenance between adjacentfilaments within each layer of an average clearance substantially equalto at least one-half the diameter of the particular filament beingwound. This spacing in relation to the selected range of filament sizeand the extent of the undercut beneath the filament sides applicable tofilaments within that range provides an access opening sufficient forthe matrix metal to be deposited solidly around and beneath thefilaments using the practical deposition procedures herein described.

A further condition found necessary for superior results is the creationduring the winding and depositing sequence of an average clearancebetween successive layers of filaments such that the filaments in suchlayers are spaced apart at their closest points a distance substantiallyequal to at least one-half the filament diameter. This is done byregulating the quantity of matrix metal deposited on and around a givenlayer before the next layer is applied to the form. By this means, asolid base is laid down for the next layer and aggravation of theproblem of getting the metal into the included spaces beneath thefilament sides is avoided.

Related to the just-described clearances maintained between thefilaments in all directions within the composite is an over-alllimitation on the proportion of the total volume of the composite thatcan be constituted by the reinforcement filaments. Thus, for purposes ofthis invention the volume ration of the filaments to the over-allcomposite cannot exceed about 0.6/1 and specific spacings for specificfilaments are to be chosen so as to meet this criterion.

While it is preferred for best results that the layers of filaments beso wound that the filaments in each layer are arranged in alternating orstaggered relation to the filaments in adjacent layers, this arrangementis not critical, and the filaments could be in general alignment in theradial or transverse direction.

The composite structures produced by the invention are useful for manypurposes in the condition as formed and further treatments such asmolding or consolidation by heat and/or pressure, while not excluded ifdesired for particular circumstances, are not essential to a usefulproduct.

Mention has already been made of the availability of several differentdeposition procedures for the production of the present composites.Examples of various techniques with respect to four different matrixmaterials are provided as follows for illustrative purposes:Electroplated Nickel:

40 oz/gal nickel sulfamate 4 oz/gal nickel chloride 4 oz/gal boric acidTemp.: l00-l40 F.

Cathode current density: 10-300 amps/ft 40 oz/gal nickel sulfate 10oz/gal nickel chloride 5 oz/gal boric acid Temp.: l00l50 C.

Cathode current density: 10-300 amps/ft 40 oz/gal nickel fluoborate 2.Vapor deposition from a cyclopentadienyl.

4 oz/gal boric acid What is claimed is: I

pH 1-3 l. The process of making composite structures com- Temp.: l-170C. prising a metallic matrix having reinforcing filaments Cathodecurrent density: 100-500 amps/ft 5 embedded therein, including the stepsof: Vapor-Plated Nickel: a. winding a reinforcement filament having adiame- Nickel carbonyl passed over substrate mandrel at'40 ter generallywithin the range of about 5-200 mito 200 C. crons onto a form insuccessive layers in which the Electroplated Cobalt-Tungsten: adjacentfilaments in each layer are spaced apart 40-70 g/l sodium tungstrate anaverage distance substantially equal to one-half 4-12 g/l cobalt sulfateof the filament diameter, and

7-150 g/l citric acid b. either concurrently with the formation of each50 g/l ammonium chloride layer or in alternation therewith depositingthe mapl-I 7-8.5 trix metal in situ around the filaments in said layerCathode current density: 50-200 amps/ft in sufficient quantity that thefilaments in adjacent Electroplated Aluminum: layers are spaced apart attheir closest points an av- 3 molar aluminum chloride erage distancesubstantially equal to about one-half 1 molar lithium aluminum hydrideof the filament diameter, the total amount of madiethyl solvent trixmetal deposited being such that the ratio of the Cathode currentdensity: 5-100 amps/ft volume of filaments to the total volume of thecom- Vapor-Plated Aluminum: posite structure does not exceed about0.6/1.

An aluminum alkyl (triisobutylaluminum) passed 2. The process of claim Iwherein said filaments are over a heated substrate at 250 C. conductiveand the matrix metal is deposited by elec- Vacuum-Evaporation ofAluminum: troplating.

Heating in a crucible. 3. The process of claim 1 wherein said form isrotated Spraying Aluminum: to wind the filament thereon and the filamentis mainl. Plasma spraying, or tained under tension during the winding.

2. Gas-torch metal spraying 4. The process of claim 1 wherein saidfilament has Titanium Deposition: a diameter of at least about 1 mil.

1. Vacuum evaporation, or

